Needle thread monitor to avoid runout of bobbin thread

ABSTRACT

An attachment for any type of lock stitch sewing machine for monitoring the amount of needle thread used by the stitching mechanism of the sewing machine so as to avoid the run out of bobbin thread from a bobbin having a known supply of bobbin thread while a workpiece is being sewn. For repetitive type of sewing, a relationship is determined between the consumption of needle thread and the consumption of bobbin thread which is required to complete a workpiece. Based on this relationship, a bobbin winding device including a counting wheel and a bobbin thread counter is provided for winding a bobbin to its maximum capacity with a known supply of bobbin thread. Also based on this relationship, a needle thread monitor including a needle thread counter and counting wheel are provided and the needle thread counter is set to terminate operation of the stitching mechanism just prior to the runout of the known supply of bobbin thread which has been wound on the bobbin. The operator is thereby warned that there is only enough bobbin thread remaining to override the automatic termination of the stitching mechanism and finish the workpiece being sewn. During operation of the sewing machine, the bobbin winding device winds the next bobbin to be used with the same amount of bobbin thread so that it may replace the depleted bobbin and be used to complete the same amount of workpieces.

United States Patent [191 Mayer et al.

1 1 'Sept. 3, 1974 NEEDLE THREAD MONITOR TO AVOID RUNOUT OF BOBBIN THREAD [76] Inventors: Nathan Mayer, 27 Messler St., East Brunswick, NJ. 08816; Anthony P. Sorrentino, 745 Woodlawn Ave., Hammonton, NJ. 08037 [22] Filed: May 11, 1973 [21] Appl. No.: 359,467

[52] US. Cl 112/219 R [51] Int. Cl D05b 69/36 [58] Field of Search 112/219 R, 219 A, 218 R,

Primary Examinerll. Hampton Hunter Attorney, Agent, or Firm--Amster & Rothstein 57] ABSTRACT An attachment for any type of lock stitch sewing machine for monitoring the amount of needle thread used by the stitching mechanism of the sewing machine so as to avoid the run out of bobbin thread from a bobbin having a known supply of bobbin thread while a workpiece is being sewn. For repetitive type of sewing, a relationship is determined between the consumption of needle thread and the consumption of bobbin thread which is required to complete a workpiece. Based on this relationship, a bobbin winding device including a counting wheel and a bobbin thread counter is provided for winding a bobbin to its maximum capacity with a known supply of bobbin thread. Also based on this relationship, a needle thread monitor including a needle thread counter and counting wheel are provided and the needle thread counter is set to terminate operation of the stitching mechanism just prior to the runout of the known supply of bobbin thread which has been wound on the bobbin. The operator is thereby warned that there is only enough bobbin thread remaining to override the automatic termination of the stitching mechanism and finish the workpiece being sewn. During operation of the sewing machine, the bobbin winding device winds the next bobbin to be used with the same amount of bobbin thread so that it may replace the depleted bobbin and be used to complete the same amount of workpieces.

12 Claims, 9 Drawing Figures PATENTED SEP 31974 sum 10F FIG. I.

Y PATENTEDSEP 3,882,960

SHEET 30F 3 FIGS.

NEEDLE THREAD MONITOR To AVOID RUNOUT OF BOBBIN THREAD The present invention relates generally to sewing machines and, in particular, to a needle thread monitor which monitors the consumption of needle thread to predict the imminent run out of bobbin thread and automatically shut off the sewing machine to avoid bobbin thread runout.

In a typical lockstitch sewing machine, the stitching mechanism includes a needle which is movable through a stitch-forming stroke and carries a needle thread into position for engagement with a bobbin thread. Typically, the bobbin thread is wound on a bobbin which is contained within a bobbin case which is removably mounted in the bobbin assembly of the sewing machine. The bobbin thread emerges from the bobbin, passes beneath a tensioning spring and is then engaged by the-needle thread as the hook of the bobbin mechanism rotates to form successive stitches.

Various techniques have been described and suggested over the years for sensing the imminent runout of the bobbin thread to thereby signal the machine operator that the bobbin supply must be replenished by removing the bobbin case and replacing the empty bobbin with a fresh bobbin. For example, it has been suggested in the art to provide the bobbin thread itself with either a mechanical or electrical indicator (i.e., an enlargement or conductive segment) at a location removed from the inner end of the wound bobbin which, upon being sensed, would signal the operator of the imminent runout of the bobbin thread supply and/or initiate a control function. Obviously, altering the characteristics of the bobbin thread in some manner introduced a complexity and cost factor which is undesirable.

Other techniques have been proposed for sensing runout of bobbin thread, but these do not have the essential attributes of reliability and repeatability such that the monitoring or sensing device will function without any false indications and will signal each and every imminent bobbin thread runout. For example, it has also been suggested in the art to employ the tensioning spring as a sensing device which, upon the runout of bobbin thread, will make electrical contact with the bobbin case and complete a circuit to an alarm system which warns the operator of the imminent runout of bobbin thread. Although such a system works quite well from a mechanical and an electrical standpoint, in practice, sewing machine operators do not clean sewing machines until they actually stop. Accordingly, the accumulation of dirt, lint, etc., around the bobbin case causes misfirings and/or malfunctions of the tensioning spring acting as a sensing device.

Further, it is important in a system of this kind to provide a runout signal and to interrupt the stitching operation before a stitch is'missed and with at least a short tail of bobbin thread extending from the last completed stitch. lf bobbin thread runout is sensed under these conditions, when the supply of bobbin thread is replenished, the operator is capable of picking up the stitch line such that there is little or no tell-tale evidence of the runout of the bobbin thread and the replenishment thereof.

Broadly, it is an object of the present invention to provide a needle thread monitoring or sensing device realizing one or more of the aforesaid objectives. Specifically, it is'within the contemplation of the present invention to provide a needle thread monitor which monitors the consumption of needle thread and provides a signal to predict the imminent runout of bobbin thread, which signal may be employed to terminate operation of the sewing machine.

It is a further object of the present invention to provide a needle thread monitor which, although simple in construction and operation, is higly reliable such that it may be used with a high degree of confidence on the vast number of industrial sewing machines which require periodic bobbin thread replenishment.

It is a still further object of the present invention to provide a bobbin winding device which will automatically wind a predetermined amount of bobbin thread onto a bobbin so that the bobbin may be employed with the needle thread monitor to predict the runout of bobbin thread from the bobbin.

In accordance with an illustrative embodiment demonstrating objects and features of the present invention, there is proivded an arrangement for monitoring the needle thread in order to predict the imminent runout of bobbin thread. This arrangement is based on the fact that in a repetitive type of sewing operation there is a definite relationship between the consumption of needle thread and the consumption of bobbin thread. Accordingly, by determining this relationship (e. g., one and one-half units of needle thread consumed for every one unit of bobbin thread consumed) and monitoring the amount of needle thread which has been consumed, it is possible to predict, based on this relationship, when a known supply of bobbin thread will run out. Further, not only does this arrangement avoid the runout of bobbin thread, but it insures that there is enough bobbin thread to allow the sewing machine operator to complete the stitching of a particular piece of work without having to change an empty bobbin during the middle of the piece of work.

More particularly, the conventional lock stitch sewing machine has been modified to include a needle thread monitor for monitoring the consumption of needle thread, a bobbin winding device for winding 21 known supply of bobbin thread onto a bobbin, means responsive to the bobbin winding device for terminating the bobbin winding operation and means responsive to the needle thread monitor for terminating operation of the sewing machine. The bobbin winding device includes a bobbin thread counter for setting a predetermined amount of bobbin thread to be wound on a bobbin and a bobbin thread counting wheel which monitors each unit of bobbin thread as it is wound onto the bobbin. When the predetermined amount has been wound onto a bobbin, the bobbin thread counter automatically terminates the bobbin winding operation. Each bobbin which is wound during a sewing cycle with the predetermined or known supply of bobbin thread, may then be used in conjunction with the needle thread monitor during the next cycle of operation. The needle thread monitor includes a needle thread counter for presetting the amount of needle thread to be used by the sewing machine in relation to the known supply of bobbin thread, and a needle thread counting wheel for monitoring each unit of needle thread which is used by the sewing machine. When the preset amount of needle thread has been used by the sewing machine, the needle thread counter terminates operation of the sewing machine by deenergizing a stop solenoid.

In accordance with the principles of the present invention, if there is a one-to-one consumption of needle thread and bobbin thread, the needle thread counter will be preset for the sewing machine to consume an amount of needle thread which is slightly less than the known amount of bobbin thread which has been wound on the bobbin by the bobbin winding device of the present invention. When the operation of the sewing machine is automatically terminated by the needle thread counter reaching its preset amount, it indicates to the operator that there is only enough bobbin thread remaining on the bobbin to complete the workpiece being sewn. The operator will then override the automatic shutoff and finish the workpiece being sewn with the remaining bobbin thread. During the sewing operation, the bobbin winding device of the present invention winds the next bobbin with a known supply of bobbin thread so that the depleted bobbin may be replaced with the newly wound bobbin and another sewing cycle may take place. To begin a new cycle, the operator merely replaces the depleted bobbin, resets the bobbin thread counter and the needle thread counter, and places the depleted bobbin on the bobbin winding device.

The above description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of a presently preferred, but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. I is a diagramatic view of the overall system of the present invention;

FIG. 2 is an elevational view in detail of the stop solenoid shown in FIG. 1;

FIG. 3 is a schematic diagram of a typical, but simplifled sewing machine control of the present invention;

FIG. 4 is a top plan view, with the sewing machine broken away, showing the needle thread monitor of the present invention;

FIG. 5 is a side elevational view of the needle thread monitor of the present invention, with the sewing machine broken away;

FIG. 6 is an end elevational view of the bobbin winding mechanism of the present invention;

FIG. 7 is a plan view, with the top broken away, of the bobbin winding device of the present invention;

FIG. 8 is a side view, with the side wall partially broken away, of the bobbin winding device of the present invention; and

FIG. 9 is a sectional view, taken along line 9-9 of FIG. 8 to illustrate in detail the bobbin winding device of the present invention.

Referring now to FIG. I, there is shown a typical lock stitch sewing machine, generally designated by the reference numeral 10, which is provided with the novel attachments of the present invention. More particularly, as will be explained below, these attachments include a solenoid-operated latch mechanism 38 (FIG. 2), a needle thread monitor 52 (FIGS. 4 and 5), a bobbin winding device 54 to supplement a conventional bobbin winding mechanism 56 (FIGS. 6 to 9) and a control box 58 (FIG. 3).

By way of background, the conventional lock stitch sewing machine 10 includes a sewing machine body 12 supported on a machine table 14. Sewing machine 10 is driven in a conventional manner by a suitable motor 16 having a clutch-brake assembly 18 at one end thereof. Clutch-brake assembly 18 is provided with an output shaft 20 having a drive pulley 22 mounted thereon to drive a sewing machine pulley 24 via a drive belt 26. Sewing machine pulley 24 is fixedly mounted on and rotates a shaft 28 and, through a conventional drive as is well known in the art, operates a stitching mechanism 30.

Clutch-brake assembly 18 is operated by an L- shaped, clutch-brake arm 32 which is connected to an operator-controlled foot treadle 40. More particularly, clutch-brake arm 32 is pivoted at 32a on a bracket 34 attached to clutch-brake assembly 18. One end 32b of clutch-brake arm 32 is connected to operate clutchbrake assembly 18 between an engaged position in which motor 16 is connected to drive stitching mechanism 30 of sewing machine 10, and a disengaged position which disconnects motor 16 from driving sewing machine 10 and is thereby shut off. In the engaged position, output shaft 20 is driven by motor 16 and the brake of clutch-brake assembly 18 is released. In the disengaged position, output shaft 20 is disconnected from motor 16 and the brake of clutch-brake assembly 18 is set so that the operation of stitching mechanism 30 is immediately shut off. The other end 32c of clutchbrake arm 32 is connected by a suitable link 36 to the solenoid-operated latch mechanism 38, forming a part of the present invention and described in detail hereinafter, which is connected to foot treadle 40 via a suitable link 42. Clutch-brake arm 32 is also provided with a link 44 having a spring 46 mounted thereon which normally biases clutch-brake arm 32 to shift clutchbrake assembly 18 from the engaged position (solid lines FIG. 1) to the disengaged position (dotted lines FIG. 1) to terminate operation of the sewing machine.

Accordingly, it should be clear that when the operator of sewing machine 10 engages foot treadle 40 in a downward direction to operate the sewing machine (see SEW position of FIG. 1), clutch-brake arm 32 is pivoted in a counterclockwise direction about pivot 32a, from the dotted line position to the solid line position of FIG. 1, and thereby shifts clutch-brake assembly 18 to the engaged position while at the same time compressing spring 46. As a result, with the clutch-brake assembly 18 in the engaged position, output shaft 20 will drive the sewing machine 10 and stitching mechanism 30, as explained above, so that a sewing operation may be performed. When the operator removes his foot from foot treadle 40, spring 46 automatically biases clutch-brake arm 32 to pivot in a clockwise direction about pivot 32a to the dotted line position, and shifts clutch-frame assembly 18 into its disengaged position. In this manner, the operation of stitching mechanism 30 is terminated manually by the operator (see STOP MAN. position in FIG. 1).

In accordance with the present invention, the abovedescribed conventional lock stitch sewing machine has been modified by the attachment of the solenoidoperated latch mechanism 38. As shown most clearly in FIG. 2, latch-mechanism 38 includes a stop solenoid 38a having an armature 38b attached to link member 36. Stop solenoid 38a is electrically connected to control box 58 via a suitable lead 380. When solenoid 38a is energized or in its ON position in FIG. 2, armature 38b is retracted and clutch-brake arm 32 and foot treadle 40 are in the dotted line position or ON position in FIG. 1. When the operator desires to sew and engages foot treadle 40, foot treadle 40 and clutch-brake arm 32 are shifted from the ONposition to the SEW position in FIG. 1. As will be explained below, control box 58 will operate to deenergize stop solenoid 380 so that armature 3812 will be extended and thereby automatically increase the distance between clutchbrake arm 32 and foot treadle 40. Accordingly, even if the operators foot is engaging foot treadle 40 to drive sewing machine 10, when solenoid 38a is deenergized, armature 38b will be extended and allow clutch-brake arm 32, under the bias of spring 46, to pivot in a clockwise direction to shift the clutch-brake assembly 18 to its disengaged position and automatically discontinue operation of the sewing machine (see STOP AUTO. position in FIG. 1).

In accordance with the present invention, the conventional lock stitch sewing machine has also been modified to include the novel attachment of needle thread monitor 52. As may be seen in FIG. 1, a spool 64 of top thread or needle thread is suitably mounted on a support and is supplied, via needle thread monitor 52 of the present invention, to the needle slot 120 of the sewing machine 10. As may be seen most clearly in FIGS. 4 and 5, the needle thread monitor attachment 52 of the present invention may be easily mounted on sewing machine body 12. More particularly, the needle thread monitor attachment 52 includes a supporting plate 66 and means for suitably mounting supporting plate 66 on sewing machine body 12, such as by screw 68. Mounted above supporting plate 66 is a bracket 70 which is mounted on supporting plate 66 by any suitable mounting means, such as by screws 72. Supporting plate 66 and bracket 70 support a rotating shaft 74 and suitable thread guide 76a and 76b. Mounted for rotation on shaft 74 is a one-lobecam 78, located between supporting plate 66 and bracket 70, and a rotating, needle thread counting wheel 80 mounted above bracket 70. In this illustrative embodiment, counting wheel 80 measures exactly one-tenth of a yard in circumference, and the needle thread wraps around and rotates counting wheel 80 as stitching mechanism draws needle thread from spool 64, A suitable microswitch 82 is also mounted between supporting plate 66 and bracket 70, and microswitch 82 is provided with a spring-biased arm 82a for engaging one-lobe cam 78. Microswitch 82 is electrically connected via a suitable lead 84 (see FIG. 3) to a needle thread counter 60 located within control box 58. Accordingly, as will be explained below, as one-tenth of a yard of needle thread is used on each rotation of counting wheel 80, cam 78 actuates microswitch 82 which in turn sends a signal or pulse to needle thread counter 60. Each signal indicates that one-tenth of a yard of needle thread has been consumed by stitching mechanism 30.

In accordance with the present invention, the conventional lock stitch sewing machine has also been modified to include the novel bobbin winding device 54 as an attachment to the conventional bobbin winding mechanism 56. Referring now to FIGS. 6 through 9, and in particular to FIG. 6, there is shown the conventional bobbin winding mechanism56 which is driven by drive belt 26. More particularly, a spool 90 of bobbin thread is suitably mounted on machine table 14 by any v suitable mounting means 92. Bobbin thread is wound on a bobbin via suitable thread guides 94 and bobbin winding device 54 which includes a bobbin thread counting wheel 96 and a thread feeder guide 98, which will be described in detail below. As in conventional bobbin winding mechanisms, bobbin 100 is mounted on a winding shaft 102 which also supports a winding wheel 104 operable to be driven by drive belt 26. Winding wheel 104 is manually shifted by the operator from a position out of engagement with drive belt 26 (dotted line position shown in FIG. 6) to a position into engagement with drive belt 26 (solid line position shown in FIG. 6). In a manner to be explained below, a solenoid-operated push rod 106 engages a release bracket 106a to automatically shift winding wheel 104 out of engagement with drive belt 26. In order to shift winding wheel 104 between these two positions, a linkage system 108 is provided which is connected to winding shaft 102. Linkage system 108 includes supporting brackets 110, 112, which are fixedly mounted on sewing machine table 14, and link members 114, 116 which are pivotally attached to supporting brackets 110, 112. In addition, a link member 118 is pivotally attached to link member 114 at one end and winding shaft 102 at the other end.

As may be seen most clearly in FIGS. 7 through 9, bobbin thread 90 is wrapped around and rotates counting wheel 96 as the bobbin thread is pulled by the bobbin winding mechanism 56. Counting wheel 96 may be of any suitable size, but in the illustrative embodiment of the present invention, the circumference of counting wheel 96 is one-tenth of a yard. Counting wheel 96 is mounted on a rotating shaft 122 which is suitably journalled in bobbin winding housing 540. A worm gear 124 is also mounted on rotating shaft 122 and drives a worm wheel 126. In the illustrative embodiment of the present invention, worm gear 124 drives worm wheel 126 at a ratio of 30 to 1 (see FIG. 3).

As may be seen most clearly in FIGS. 3 and 8, worm wheel 126 is mounted for rotation on a shaft 128 which is also joumalled in bobbin winding housing 54a. A three-lobe cam 130, having its three lobes apart, is also mounted for rotation on shaft 128 for engaging a microswitch 132, having a spring-biased arm 132a. Accordingly, microswitch 132 is actuated each time it is engaged by one of the lobes of cam and sends a signal or pulse via an electrical lead 134 (see FIG. 3). to a bobbin thread counter 62 in control box 58. Each signal indicates that one yard of bobbin thread has been wound on bobbin 100.

When bobbin thread counter 62 reaches a preset amount, it will energize a solenoid 138 via an electrical lead 136 (see FIG. 3). As shown most clearly in FIG. 8, when solenoid 138 is energized, its armature 140 is retracted and drives push rod 106 in the direction of the arrow shown in' FIG. 8. Push rod 106 is driven against the bias of a spring 142 to engage release bracket 106a mounted on linkage system 108 so that bobbin winding mechanism 56 and winding wheel 104 are automatically shifted to the dotted line position (see FIG. 6) and out of engagement with drive belt 26. When this occurs, a preset amount of bobbin thread 90 has been wound onto bobbin 100 and is ready for use by the operator, as will be explained below.

In order to reset the bobbin thread counter 62 to zero so that the next bobbin 100 may be wound with bobbin thread, a reset switch is also provided in bobbin winding housing 540. As may be seen most clearly in FIG. 8, when armature 140 is retracted, it actuates .reset switch 150 via a switch arm 150a. As shown in FIG. 3, reset switch 150 via a lead 152, then operates to reset bobbin thread counter 62 to zero for the next bobbin winding operation.

Bobbin winding housing 54a is also provided with a feeder guide 98 to insure that bobbin thread 90 is uniformly wound on bobbin 100. As may be seen in FIGS. 7 and 8, a cam 154 is mounted for rotation on shaft 128. Cam 154 is situated between two extension rods 98a, 98b extending from feeder guide 98. Accordingly, as shaft 128 and cam 154 rotate, cam 154 alternately engages extension rods 98a, 98b so as to reciprocate feeder guide 98 back and forth as shown by the arrow in FIG. 7. In this manner, feeder guide 98 moves bobbin thread 90 back and forth so that it may be uniformly wound on bobbin 100.

Turning now to FIG. 3 of the drawings, there is shown an overall control diagram of the present invention including the novel attachments to the conventional sewing machine 10. As mentioned above, control box 58 includes needle thread counter 60 and bobbin thread counter 62. In order to set the needle thread counter 60 to a preset amount, control box 58 is provided with dials 60a and 60b, and in order to set bobbin thread counter 62 to a preset amount, control box 58 is also provided with dials 62a and 62b. In addition, control box 58 includes an on-off power switch 58a, and an indicator light 58b which indicates that bobbin thread counter 62 has been automatically reset to zero by reset switch 150. Further, control box 58 includes a reset switch 58c for resetting needle thread counter 60 to zero, as will be explained, and a digital indicator 5811 which provides a running indication of the amount of needle thread which has been consumed at any given time.

A specific example employing the sewing machine of the present invention will now be illustrated. In accordance with the principles of this invention, it has been found that there is a fixed relationship between the consumption of needle thread and the consumption of bobbin thread for any given workpiece. Accordingly, a trial run may be made with a particular workpiece in order to determine this relationship. For simplicity, we will assume that a particular one-ply workpiece to be stitched consumes an equal amount of bobbin thread and needle thread, i.e., there is a one-to-one relationship between the consumption of needle thread and the consumption of bobbin thread. We will also assume that as a result of the trial run, it has been determined that each workpiece to be sewn requires 2 yards of bobbin thread and 2 yards of needle thread. Accordingly, if the maximum capacity of bobbin 100 is 45 yards and it is desired to avoid the runout of bobbin thread in the middle of sewing a workpiece, the stitching operation must be terminated after 43 yards of bobbin and needle thread have been consumed, in order to insure that 2 yards of bobbin thread remain to complete the last workpiece. Therefore, in accordance with the present invention, the operator will use dials 62a, 62b to set bobbin thread counter 62 for 45 in order to wind 45 yards on each of the bobbins 100. In addition, the operator will also use dials 60a, 60b to set needle thread counter 60 to 43 yards. By setting bobbin thread counter 62 for'45 yards so that the maximum of 45 yards of bobbin thread will be wound on each bobbin 100, it will insure that each bobbin is used to its full capacity and that there is always enough bobbin thread or a bobbin tail in case there are any variations in winding the bobbin thread or any variations in its consumption. In addition, by setting needle thread counter 60 to 43 yards, it will operate to shut off the sewing machine 10 automatically after 43 yards of needle thread and after 43 yards of bobbin thread have been consumed, i.e., approximately in the middle of the twenty-second workpiece. When the sewing machine stops, the operator then knows that there is only enough bobbin thread remaining (2 yards, i.e., 45 yards-43 yards) to complete the workpiece being sewn (twenty-second workpiece of 2 yards) and have a short bobbin tail left over of approximately one yard of bobbin thread. Of course, even if the operator has made only a few stitches in the last workpiece, there would still be enough bobbin thread to complete that workpiece, without having to change bobbins in the middle of the workpiece. Accordingly, to complete the last workpiece, the operator overrides the automatic shutoff of the sewing machine by actuating reset switch 580 and depressing treadle 40 which shifts clutchbrake assembly 18 to its engaged position. To start a new sewing cycle, the operator merely removes the depleted bobbin and supplies it with a new bobbin 100 which has been wound by the bobbin winding device 54 with 45 yards of bobbin thread, actuates reset switch 58c to reset needle thread counter 60 to zero, sets needle thread counter 60 for 43 yards again, sets bobbin thread counter 62 for 45 yards and places the-depleted bobbin 100 on a bobbin winding device 54 to be wound.

Referring now specifically to FIG. 3, and in accordance with the above example, bobbin thread counter 62 is set for 45 yards and needle thread counter 60 is set for 43 yards. As each one-tenth of a yard of needle thread is consumed and passes around counting wheel 80, cam 78 and microswitch 82 will operate via lead 84 to send a signal or pulse to needle thread counter 60 in control box 58. When needle thread counter 60 registers that 43 yards of needle thread have been consumed, control box 58 will operate to deenergize stop solenoid 38a via lead 380. When stop solenoid 38a is deenergized, armature 38d will be extended and allow clutch-brake arm 32 to pivot in a clockwise direction to shift the clutch-brake assembly 18 to its disengaged position and automatically discontinue the stitching operation of sewing machine 10 (see STOP AUTO position in FIG. 1) even though the operator has his foot engaging treadle 40. The operator then actuates reset switch 580 to reset needle thread counter 60 to zero and depress treadle 40 to override the automatic shutoff. In this manner, stop solenoid 38a will again be energized via lead'38c to retract armature 38b so that sewing machine l0may be operated. Accordingly, the

operator has been warned that there is only enough bobbin thread remaining on bobbin'l00 to complete the workpiece presently being stitched. At the end of stitching that workpiece, the operator must replace the depleted bobbin 100 with a new supply of bobbin thread, which may be either a prewound bobbin with a known supply of bobbin thread or a bobbin wound with a known supply of bobbin thread on a suitable bobbin winding device.

Accordingly, the present invention also includes bobbin winding device 54. In accordance with the above example, the operator may employ bobbin winding device 54 to wind 45 yards of bobbin thread on each bobbin 100 to be used with the needle thread monitor 52 of the present invention. In order to wind the required 45 yards of bobbin thread on a bobbin 100, an empty bobbin 100 is placed on shaft 102, and Winding wheel 104 is manually shifted into engagement with drive belt 26. Accordingly, as the operator is sewing with a previously wound bobbin, winding wheel 104 will operate to wind bobbin thread onto depleted bobbin 100. With each yard of bobbin thread that is wound onto bobbin 100, counting wheel 96, worm gear 124, worm wheel 126, three-lobe cam 130, and microswitch 132 operate via lead 134 to signal bobbin thread counter 62 in control box 58 that one yard of bobbin thread has been wound onto bobbin 100. Accordingly, when the bobbin thread counter 62 registers that the required 45 yards of bobbin thread have been wound on bobbin 100, control box 58 will energize solenoid 138 via lead 136 to retract armature 140, armature 140 drives push rod 106 to engage release bracket 106a so that linkage system 108 will operate to shift winding wheel 104 out of engagement with drive belt 26 and terminate the winding operation. As the winding of bobbin thread takes place extremely fast as compared to the consumption of needle thread, the 45 yards of bobbin thread will be wound on bobbin 100 in a fraction of the time that it takes to consume the 45 yards of bobbin thread wound on the bobbin 100 which is being used. When solenoid 138 is energized, armature 140 also operates to actuate reset switch 150 which sends a signal via lead 152 to control box 58 to reset bobbin thread counter 62. (As explained above, needle thread counter 60 is reset manually by the operator actuating reset switch 580 so that the operator may manually override the automatic shutoff of the sewing machine in order to complete the last workpiece). In this manner, a new known supply of bobbin thread is ready for the next group of workpieces to be sewn.

The above illustrative example is based upon a oneto-one consumption of needle thread and bobbin thread. However, if a two or three-ply workpiece is being sewn, a trial run may indicate that 1%: yards of needle thread are consumed for every yard of bobbin thread on each workpiece. Accordingly, 67.5 yards of needle thread will be consumed for every 45 yards of bobbin thread consumed. The bobbin thread counter 62 will again be preset to wind the maximum number of yards of bobbin thread onto bobbin 100, i.e., the bobbin thread counter 62 will be preset to wind 45 yards onto bobbin 100. In addition, the needle thread counter 60 will also be preset to automatically shut off the sewing machine with enough bobbin thread remaining to complete the last workpiece being sewn. Accordingly, if each workpiece requires 2 yards of bobbin thread and 3 yards of needle thread, the needle thread counter 60 will be set to shut off the sewing machine, in the manner explained above, after 43 yards of bobbin thread have been consumed and after 64.5 yards of needle thread have been consumed. The operator then manually actuates reset switch 580 and depresses treadle 40 to override the automatic shutoff, knowing that there is only enough bobbin thread (2 yards) remaining to complete the last workpiece.

Accordingly, the present invention solves two major problems:

1. By monitoring the consumption of needle thread and terminating the sewing operation after the preset number of yards of needle thread have been consumed, it avoids the runout of bobbin thread on the bobbin wound with a known supply of bobbin thread. In other words, without the monitoring device of the present invention, the operator in the first example illustrated above would have begun sewing the twenty-third piece of work which would have required 46 yards of bobbin thread when there wasonly 45 yards wound on'bobbin 100. Or, if there were an unknown amount of bobbin thread on the bobbin, as is normally the case, the operator would merely continue sewing until he noticed that the bobbin thread supply had run out, which would most likely occur while a workpiece was being sewn. This would result in defective stitches to be pulled out and the sewing retraced, or discarding of the defectively sewn workpiece.

2. The present invention also avoids the need for changing bobbins in the middle of stitching a workpiece.

A latitude of modification, change and substitution is intended in the foregoing disclosure without departing from the spirit and scope of the invention herein. For example, in the needle thread monitor 52, it is possible to employ other types of switching arrangements instead of cam 78 and microswitch 82. More particularly, a Hall effect switch may be mounted on needle thread counting wheel 80 which operates by means of rotating a permanent magnet through its field, and as the south pole of the magnet sweeps through the field, the normal voltage of the device drops to zero and would provide an output signal from the Hall effect switch to the needle thread counter 60 in control box 58. In addition, various modifications may be made to the embodiment of the bobbin winding device 54 disclosed herein. More particularly, worm gear 12 4, cam and microswitch 132 may be replaced with a similar Hall effect switch mounted on bobbin thread counting wheel 96 to operate as previously described, in order to provide an output signal from the Hall effect switch to the bobbin thread counter 62 in control box 58. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What is claimed is:

l. The method of sensing thread runout in a sewing machine including a stitching mechanism which performs a stitching operation with a needle thread and bobbin thread wound on a bobbin by monitoring the needle thread to predict the runout of the bobbin thread comprising the steps of measuring the amount of bobbin thread wound on said bobbin, monitoring the unwinding of bobbin thread from said bobbin by measuring each unit of needle thread used by said stitching mechanism, providing a termination signal when the measurement of needle thread indicates the imminent runout of bobbin thread from said bobbin and, before said bobbin runs out of bobbin thread, terminating operation of said stitching mechanism in response to said termination signal.

2. The method of claim 1 wherein the step of measuring the bobbin thread includes the steps of drawing the bobbin thread about a rotatable device and signalling a counter in response to rotation of said device.

3. The method of claim 1 wherein the step of monitoring the unwinding of bobbin thread from said bobbin includes the steps of drawing the needle thread about a rotatable device and signalling a counter in response to rotation of said device.

4. The method of claim 3 wherein the step of providing a termination signal includes the steps of presetting said counter with the amount of needle thread to be used by said stitching mechanism in relation to the amount of bobbin thread wound on said bobbin and signalling said counter as each unit of needle thread is measured until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin.

5. The method of monitoring the needle thread of a sewing machine to predict the runout of bobbin thread from a bobbin, said sewing machine including a stitching mechanism for performing a stitching operation comprising the steps of measuring the amount of bobbin thread wound on said bobbin, presetting a counter with the amount of needle thread to be used by said stitching mechanism in relation to the amount of bobbin thread wound on said bobbin, measuring each unit of needle thread used by said stitching mechanism to thereby monitor the unwinding of bobbin thread from said bobbin, signalling said counter as each unit of needle thread is measured until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin, and, before said bobbin runs out of bobbin thread, terminating operation of said stitching mechanism in response to said counter reaching coincidence.

6. A sewing machine adapted to receive a supply of needle thread and a bobbin containing a supply of bobbin thread, said sewing machine including a stitching mechanism for performing a stitching operation utilizing said needle and bobbin threads comprising means for measuring the amount of bobbin thread wound on said bobbin, a counter for presetting the amount of needle thread to be used by said stitching mechanism in relation to'the amount of bobbin thread wound on said bobbin, means for monitoring each unit of needle thread which is used by said stitching mechanism to thereby monitor the use of bobbin thread from said bobbin, means connected to said monitoring means for signalling said counter as each unit of needle thread is used until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin, means responsive to said counter reaching coincidence for terminating operation of said stitching mechanism before said bobbin runs out of bobbin thread.

7. A sewing machine in accordance with claim 6 wherein said monitoring means includes a rotatable wheel, said needle thread being operable to rotate said rotatable wheel as the stitching mechanism draws needle thread from said needle thread supply.

8. A sewing machine in accordance with claim 7 wherein said signalling means includes a switch which is actuated in response to rotation of said rotatable wheel.

9. A sewing machine in accordance with claim 6 wherein said terminating means includes a solenoidoperated armature, said armature being operable when said solenoid is deenergized to terminate operation of said stitching mechanism.

10. In combination, a sewing machine including a stitching mechanism for performing a stitching operation utilizing a supply of needle thread and a supply of bobbin thread, and a bobbin winding mechanism for winding bobbin thread from said supply of bobbin thread onto an empty bobbin to produce a wound bobbin containing a predetermined amount of bobbin thread comprising a bobbin thread counter for setting a predetermined amount of bobbin thread to be wound on said empty bobbin before the winding operation is terminated, a needle thread counter for presetting the amount of needle thread to be used by said stitching mechanism before said wound bobbin runs out of bobbin thread and the stitching operation is terminated, first means for monitoring each unit of bobbin'thread as it is wound on said empty bobbin, second means for monitoring each unit of needle thread as it is used by said stitching mechanism, first means connected to said first monitoring means for signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, second means connected to said second monitoring means for signalling said needle thread counter as each unit of needle thread is used until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said needle thread counter thereby indicating the imminent runout of bobbin thread from said wound bobbin, means responsive to said bobbin thread counter reaching coincidence for terminating operation of said bobbin winding mechanism and means responsive to said needle thread counter reaching coincidence for terminating operation of said stitching mechanism before said wound bobbin runs out of bobbin thread.

11. The method of claim 1 further including winding a predetermined amount of bobbin thread from a supply of bobbin thread onto an empty bobbin including the steps of presetting a bobbin thread counter with a predetermined amount of bobbin thread to be wound on said empty bobbin, monitoring each unit of bobbin thread as it is wound on said empty bobbin, signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, and terminating the winding operation in response to said bobbin thread counter reaching coincidence.

12. A sewing machine in accordance with claim 6 further including a bobbin winding mechanism for winding bobbin thread from a supply of bobbin thread onto an empty bobbin including a bobbin thread counter for setting a predetermined amount of bobbin thread to be wound on said empty bobbin, second means for monitoring each unit of bobbin thread as it is wound on said empty bobbin, second means connected to said second monitoring means for signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, and means responsive to said bobbin thread counter reaching coincidence for tenninating operation of said bobbin winding mechanism. 

1. The method of sensing thread runout in a sewing machine including a stitching mechanism which performs a stitching operation with a needle thread and bobbin thread wound on a bobbin by monitoring the needle thread to predict the runout of the bobbin thread comprising the steps of measuring the amount of bobbin thread wound on said bobbin, monitoring the unwinding of bobbin thread from said bobbin by measuring each unit of needle thread used by said stitching mechanism, providing a termination signal when the measurement of needle thread indicates the imminent runout of bobbin thread from said bobbin and, before said bobbin runs out of bobbin thread, terminating operation of said stitching mechanism in response to said termination signal.
 2. The method of claim 1 wherein the step of measuring the bobbin thread includes the steps of drawing the bobbin thread about a rotatable device and signalling a counter in response to rotation of said device.
 3. The method of claim 1 wherein the step of monitoring the unwinding of bobbin thread from said bobbin includes the steps of drawing the needle thread about a rotatable device and signalling a counter in response to rotation of said device.
 4. The method of claim 3 wherein the step of providing a termination signal includes the steps of presetting said counter with the amount of needle thread to be used by said stitching mechanism in relation to the amount of bobbin thread wound on said bobbin and signalling said counter as each unit of needle thread is measured until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin.
 5. The method of monitoring the needle thread of a sewing machine to predict the runout of bobbin thread from a bobbin, said sewing machine including a stitching mechanism for performing a stitching operation comprising the steps of measuring the amount of bobbin thread wound on said bobbin, presetting a counter with the amount of needle thread to be used by said stitching mechanism in relation to the amount of bobbin thread wound on said bobbin, measuring each unit of needle thread used by said stitching mechanism to thereby monitor the unwinding of bobbin thread from said bobbin, signalling said counter as each unit of needle thread is measured until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin, and, before said bobbin runs out of bobbin thread, terminating operation of said stitching mechanism in response to said counter reaching coincidence.
 6. A sewing machine adapted to receive a supply of needle thread and a bobbin containing a supply of bobbin thread, said sewing machine including a stitching mechanism for performing a stitching operation utilizing said needle and bobbin threads comprising means for measuring the amount of bobbin thread wound on said bobbin, a counter for presetting the amount of needle thread to be used by said stitching mechanism in relation to the amount of bobbin thread wound on said bobbin, means for monitoring each unit of needle thread which is used by said stitching mechanism to thereby monitor the use of bobbin thread from said bobbin, means connected to said monitoring means for signalling said counter as each unit of needle thread is used until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said counter thereby indicating the imminent runout of bobbin thread from said bobbin, means responsive to said counter reaching coincidence for terminating operation of said stitching mechanism before said bobbin runs out of bobbin thread.
 7. A sewing machine in accordance with claim 6 wherein said monitoring means includes a rotatable wheel, said needle thread being operable to rotate said rotatable wheel as the stitching mechanism draws needle thread from said needle thread supply.
 8. A sewing machine in accordance with claim 7 wherein said signalling means includes a switch which is actuated in response to rotation of said rotatable wheel.
 9. A sewing machine in accordance with claim 6 wherein said terminating means includes a solenoid-operated armature, said armaturE being operable when said solenoid is deenergized to terminate operation of said stitching mechanism.
 10. In combination, a sewing machine including a stitching mechanism for performing a stitching operation utilizing a supply of needle thread and a supply of bobbin thread, and a bobbin winding mechanism for winding bobbin thread from said supply of bobbin thread onto an empty bobbin to produce a wound bobbin containing a predetermined amount of bobbin thread comprising a bobbin thread counter for setting a predetermined amount of bobbin thread to be wound on said empty bobbin before the winding operation is terminated, a needle thread counter for presetting the amount of needle thread to be used by said stitching mechanism before said wound bobbin runs out of bobbin thread and the stitching operation is terminated, first means for monitoring each unit of bobbin thread as it is wound on said empty bobbin, second means for monitoring each unit of needle thread as it is used by said stitching mechanism, first means connected to said first monitoring means for signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, second means connected to said second monitoring means for signalling said needle thread counter as each unit of needle thread is used until said preset amount of needle thread is used by said stitching mechanism and coincidence is reached in said needle thread counter thereby indicating the imminent runout of bobbin thread from said wound bobbin, means responsive to said bobbin thread counter reaching coincidence for terminating operation of said bobbin winding mechanism and means responsive to said needle thread counter reaching coincidence for terminating operation of said stitching mechanism before said wound bobbin runs out of bobbin thread.
 11. The method of claim 1 further including winding a predetermined amount of bobbin thread from a supply of bobbin thread onto an empty bobbin including the steps of presetting a bobbin thread counter with a predetermined amount of bobbin thread to be wound on said empty bobbin, monitoring each unit of bobbin thread as it is wound on said empty bobbin, signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, and terminating the winding operation in response to said bobbin thread counter reaching coincidence.
 12. A sewing machine in accordance with claim 6 further including a bobbin winding mechanism for winding bobbin thread from a supply of bobbin thread onto an empty bobbin including a bobbin thread counter for setting a predetermined amount of bobbin thread to be wound on said empty bobbin, second means for monitoring each unit of bobbin thread as it is wound on said empty bobbin, second means connected to said second monitoring means for signalling said bobbin thread counter as each unit of bobbin thread is wound on said empty bobbin until said predetermined amount of bobbin thread is wound on said empty bobbin and coincidence is reached in said bobbin thread counter, and means responsive to said bobbin thread counter reaching coincidence for terminating operation of said bobbin winding mechanism. 